After the adoption of the B-3, it was intended to be worn as an inner layer of the TYPE C-3 flight jacket, which was adopted in 1936 for the purpose of layering in the extremely cold heavy zone. It has a structure that prevents the hair from coming out and increases resistance.

• Sheep
• Finishing tape: horse leather/tannin tanning, aniline finishing
• Front zipper: 1940s bell type, nickel plating, cotton ribbon
• Cotton thread
• Made in Japan